There have been a few times over the past week where I have noticed scenarios of retired professionals being asked by people to teach them certain skills and knowledge. In many cases people specifically researched about them through things such as public records as in a few cases the people in question used to run schools. In many cases it made sense. Knowledge wise people were learning similar things to what they would learn from going to a commercialized school. In these cases though, they got to learn in a private setting. At the same time, it was a lot cheaper since as a retired person people were teaching it more out of passion.
That holds true in many instances in general of course when you have people who will teach you skills and knowledge because they are genuinely passionate about what they do. But in this case there are probably more odds of finding a person like this with this kind of circumstance. The drawback of course is you really need to do your research if you want to find these people. But as these examples showed me it is fully possible.